Response differences of intersegmental auditory neurons recorded close to or far away from the presumed spike-generating zone

Abstract

Intracellular recordings may give valuable information about processing of a neuron and possibly its input from the network. Impalement with an electrode causes injury to the cell and depolarization from intrusion of extracellular fluid. Thus, penetration artefacts may contaminate recordings and conceal or even alter relevant information. These penetration artefacts may have the strongest impact close to the spike-generating zone near the dendrites. Recordings in axonal portions might therefore be less vulnerable while providing insufficient information about the synaptic input. In this study, we present data of five previously identified intersegmental auditory neurons of a bushcricket independently recorded in their dendrites (prothorax) and axon (brain). Generally, responses to acoustic pulses of the same parameter combination were similar within a neuronal class at the two recording sites. However, all neuronal classes showed significantly higher response variability and a tendency for higher spike activity when recorded in the dendrites. Unexpectedly, the combined activity of two neurons (Ascending Neurons 1 and 2) recorded in the brain provides a better fit to song recognition than when recorded in the thorax. Axonal recordings of T-shaped Neuron 1 revealed graded potentials originating in the brain and modulating its output in a potentially behaviourally relevant manner.

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Acknowledgments

First, we would like to remind of the late Norbert Elsner, who supported us throughout the study. We would like to thank Silvia Gubert and Matthias Schink who helped with rearing the animals. We also like to thank Philipp Jähde for his help analysing some of the data. TDO was supported by the Marianne and Dr. Fritz Walter Fischer funding and the Göttingen Graduate School for Neurosciences and Molecular Biosciences (GGNB). We also would like to thank the reviewers for their helpful suggestions on the manuscript. Part of the study was supported by the German Science Foundation (DFG), Grant Number Stu 189/1-4. The experiments conducted in this study comply with the current laws of Germany and the “Principles of animal care”, publication No. 86-23, revised 1985 of the National Institute of Health.

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